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Output | Software Solutions | Proofing | Color, Screening and Calibration | Scanning | Digital Photography | Consumables | POS
Commands | Description | NVS Parameters | Parts | Procedures | Theory of Operation
The head stage consists of two plates. The bottom plate is mounted on the carriage and supports a linear bearing that carries the top plate (or stage), which is a platform for the thermal head.
The main functions of the head stage include:
Note: The head stage is a Field Replaceable Unit.
Installing the ThermoFlex Head Stage
Adjusting ThermoFlex Head
Adjusting ThermoFlex Head Stage Tab Settings
Replacing ThermoFlex Head Stage Stepper Motor
Replacing ThermoFlex Head Stage Stepper Motor Driver Board
Replacing ThermoFlex Head Stage Home/Away Board
Replacing ThermoFlex Head Stage Recovery Spring
The two main components in the head stage are the top plate and the bottom plate. The bottom plate is mounted on the carriage and supports a linear bearing that carries the top plate (or stage), which is a platform for the thermal head. The linear bearing allows the radial motion towards and away from the drum, and the drive is provided by a linear actuator stepper motor with an integral 40 threads per inch leadscrew. Rotation of the hollow motor shaft (rotor nut) results in linear motion of the leadscrew, when the leadscrew is prevented from rotating.
Each step of the 200 step motor gives a linear motion of 3.175um. The leadscrew is maintained in tension by a helical compression spring loading the top and bottom plates, which eliminates backlash from the drive. This spring drives the stage towards the drum, while the leadscrew restrains the stage. Depending on the direction of motion specified, the leadscrew will pull the stage away from the drum against the spring, or advance the stage towards the drum, acting like an escapement.
Mechanical stops are fitted which limit the motion of the stage if the control system fails, but in normal operation the range of motion is controlled by the Home and Away tabs on the stage. The nominal travel from Home to Away positions is 2250 steps, or 7.14mm. An additional motion feature is provided in which the stage can disengage immediately, moving away from the drum against the spring force, if a plate fly-off occurs with the plate becoming trapped between the stage and the thermal head, so limiting the load on the thermal head. This break-away motion is 23mm.
A recovery spring is fitted which enables the stage to recover mechanically from a runaway control condition where the leadscrew is driven completely out of the motor. The reserve travel from the Away mechanical stop to the leadscrew being driven out of the motor is approximately 17mm, or 5350 steps. A decoupler is fitted to the top plate and allows for alignment of the leadscrew with the motor on initial assembly.
Note: The top plate screws and both decoupler screws should never be loosened when the stage is fitted to a machine, as alignment of the stage could be lost.
When a plate is loaded and the plot command is given, the stage is driven from the Home position towards the media while the autofocus sum and error feedback numbers are read and evaluated. Focus on the media is achieved when the sum and error numbers are considered satisfactory, and the plate thickness is then calculated. When focussed on the media, the stage then remains fixed in this position and imaging is done with the autofocus servo operating as normal.
After imaging and before the plate unloads, the stage goes to the Home position for safety, until the next plot instruction is issued.